Variable relationship between chimerism and tolerance after hematopoietic cell transplantation without myelosuppressive conditioning.

Background: We have previously described a mixed chimerism protocol that avoids myelosuppressive conditioning and permits hematopoietic cell transplantation across MHC barriers without the need for whole body irradiation in miniature swine. Here, we report our current experience including animals conditioned without thymic irradiation, and we attempt to define the relationship between long-term chimerism and stable tolerance in these animals.

Methods: Recipient swine received in vivo T-cell depletion, with or without thymic irradiation on day -2.